Rotary earth-drilling system



30,1930-v 1 1. D. JAMES 1,786,755

ROTARY EARTH DRILLING SYSTEM Original Filed Dec. 23 1924 :latented Dec. 30, 1930 6 plications.

UNITED, STATES A T omen f -HENBY D. JAMES, OF EDGEWOOD PARK, PENNS'YIVANIA, ASSIGNOB TO WES'1ING- I HOUSE ELECTRIC MANUFACTURING COMPANY, A CORPORATION 01 PENNSYL- VAN IA ao'ranr m m Application filed December 88, museum Io. 757,591 lenewedlay, 81,1080.

My invention relates to systems of motor control and it has particular relation to such systems as are em loyed in connection with earth drilling mac ine tools and similar ap- An object of my invention'is to provide electrical means for varying the pressure on the working tool in accordance with the resistance met in the operation.

Certain prior systems employ mechanical devices, comprising differential-gear mechanisms, for controlling the drilling pressure in accordance with the load, whereas, in accordance with my invention the equipment is greatly simplifiedby employing two alternating-current induction motors so connected as to provide an electrical differential action.

The first motor is connected to the line through a series transformer and performs the customary drilling operation, while the second motor, which governs the feeding of the drill-bit, is responsive to line voltage and also to the current traversing the above-men tioned series transformers.

My inventionwill be best understood by reference to the ,accompanying drawing, in which Figure 1 illustrates a derrick of a familiar character that is employed in connection with rotary earth-drilling, to which my invention is applied, and

Fig. 2 is a diagrammatic representation of the scheme of main-circuit connections embodying my invention.

Referring to Fig. 1, an induction motor 1 is connected through suitable gearing to operate a rotary table 2. A drill stem 3 is rotated by means of the table and is suspended by means of a cable 4 that is wound on a hoisting drum 5, in accordance with a familiar practice. The hoisting drum maybe operated through any suitable gearing, or the like,

by means of an induction motor 6 that is preferably of the high-resistance squirrel cage yp The motor 6 operates on the principle of a torque motor, whereby itstorque is exerted in opposition to the weight of the suspended tool 3 and it thus functions as a feedi moing tor, in conjunction copending application of Frederic Hild,

filedMar. 22, 1921, Serial No.454,4 51, which application further illustrates the details of with-the gravity rea ing the rotary drilling connections and the cus tomary means of suspending the drilling tool. In accordance with my 5 stem, however,. it becomesunnecessary to urnish the differential mechanism illustrated in the aboveidentified application, v

The primary windings of the motor 1 refromline conductors 8,9 and 10 ceive enerfi v (Fig. 2) t rough primary windings 11, 12

and 13 ofcurrent-transformers that are. con;

nected in the res ective line conductors. The

feed motor 6 is a so connected to line conduc.

tors 8, 9 and 10 through primary windings'14, 15 and 160i series transformers inha manners milarto the connections for the drilling motor 1.

Wheuloadcurrent traverses the drilling motor, the currents traversing transformer windings 11,12 and 13 induce voltages in the ndingsecondary transformer wind-v 18'.and 19, which windings are concorres ingsl nectedfinlseriesor loop circuits, comprising the corresponding secondary windings 20,21 and-22, for "controlling the excitation of the drilling motor 6. The windings 14 and 20 are so related that current traversing. the winding 20 reduces the drop in otential across winding. 14, winding 21 sim arly fif'. fectsthe otentialof winding 15 fand winding,22" li ewise controls the excitation of.

winding 16, so that the excitation of the primary winding of the feed motor 6 is varied in accordance with the load imposedonthe drillingmotor 1.' 1

Under normal, operating conditions, the excitation'of the feed motor 6, and the torque thereof, is sufiicient to partially overcome the weight of the drill 3, wherebythedrill pressure (the drill thus being fed by gravlty) is determined. In the event of increased resistance being met, on account of changes injthe earth formation, thereby ime osing additional, load;on the motor l, the mid current of drillin motor 1 efiecta en increase in the excitation of the feed motor (3. which thereupon tends to proportionately raise the drill stem 3 and relieve the pressure on the drill-bit. When this pressure is relieved, the load on the drilling motor is of course reduced and in such manner a balanced condition is obtained between the two motors and a certain desirable drilling pressure is automatically maintained.

In other words, the electrical interconnections between the motors serve-to regulate the bit pressure inversely in proportion to the hardness of the formation being cut and in a case of overload, such as a jammin of the tool, the latter-is entirely retrieve or withdrawn from the work, thereby automatically relieving the overload, whereupon the tool will a ain advance to the work. It is evi ent that the torque of the feed mo tor 6 may be varied, as for example, by varying the number of active turns 0 ary windin 17 18 and 19, as indicated in Fig. 2, so t at these windings become more or less e'fi'ective in accordance with the load current and, therefore, correspondingly increase or reduce the excitation of the windings 20,21 and 22 that govern the feed motor.

have illustrated my invention in preferred form, but modifications may readily be made therein. For example the invention may be employed in 'various machinetool applications. 'Consequentl I desire that my invention shallbe limited only in accordance with the scope of the appended claims.

I claim as my invention:

1. The combination with a tool and an alternatin -current motor therefor,.provided with a p urality ofconductors for supplying energy thereto, of a second alternatin current motor for controlling the feed 0 said tool, a plurality of current transformers connected in the circuit of the first named motor, and means for connecting said transformers to increase and decrease the excitation of said second motor in accordance with the increase and decrease of the excitation of said first named motor.

2. The combination with a working tool,

of an alternating-current-motor for operating the tool, a second alternatin -current motor for feeding the tool against t e work, a source of alternating-current power for the motors, individual circuits from said source to each motor, interconnected current transformers, connected in each of saidindividual circuits, for controlling the operation of the motor for feeding the tool in response to the load current of the motor operthe second ber,'1924.

HENRY D. J AMES. 

